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.\" Author: Thomas E. Dickey
.\"
.\" $Id: legacy_coding.3x,v 1.32 2024/09/14 20:06:50 tom Exp $
.TH legacy_coding 3X 2024-09-14 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.SH NAME
\fB\%use_legacy_coding\fP \-
override \fIcurses\fR locale encoding checks
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint use_legacy_coding(int \fIlevel\fP);
.fi
.SH DESCRIPTION
.BR \%use_legacy_coding ","
an
.I \%ncurses
extension to the
.I curses
library,
permits customiztion of \fB\%unctrl\fP(3X) behavior,
suppressing \fI\%isprint\fP(3)-based checks within the library that
would normally cause nonprinting characters to be rendered in visible
form.
The alteration affects only byte-wide characters with the most
significant bit set.
.PP
The
.I level
parameter controls the result.
.RS
.TP 5
.B 0
The library functions normally,
rendering nonprinting characters as described in \fB\%unctrl\fP(3X),
.TP
.B 1
the library ignores
.I \%isprint
for codes in the range 160-255.
.TP
.B 2
the library ignores
.I \%isprint
for codes in the range 128-255.
It also modifies the output of \fB\%unctrl\fP(3X),
showing codes in the range 128-159 as is.
.RE
.SH RETURN VALUE
If the
.I curses
screen has not been initialized,
or the
.I level
parameter is out of range,
.B \%use_legacy_coding
returns
.BR ERR .
Otherwise,
it returns the previous level.
.SH EXTENSIONS
.B \%use_legacy_coding
is an
.I \%ncurses
extension.
.SH PORTABILITY
Applications employing
.I \%ncurses
extensions should condition their use on the visibility of the
.B \%NCURSES_VERSION
preprocessor macro.
.SH HISTORY
.I \%ncurses
5.6 (2006) introduced
.I \%use_legacy_coding
to support \fI\%lynx\fP(1)'s font-switching feature.
.SH AUTHORS
Thomas Dickey
.SH SEE ALSO
\fB\%unctrl\fP(3X)
